In the AT modem command set what is the opposite of +++

I'm using as USR modem on a link and have had to use the +++ command to get control of the modem to issue a command to it whilst it was dialed up ( and working ). This has worked and the command I send to the modem also worked, but what do I send to the modem to tell it to stop listening for commands and continue passing data accross the link ?